The present invention relates to an organic electroluminescence display device (hereinafter, abbreviated simply as xe2x80x9corganic EL display devicexe2x80x9d). More particularly, the invention relates to an organic EL display device that is suitably used, as a display, a light source for the printer-head, or the like, for the civil and industry uses.
As generally called a xe2x80x9cman-machine interfacexe2x80x9d, an electric display device is an electronic device for visually transmitting various information from various machines to a man and has an important role as an interface to connect a man with a machine.
As the electric device, an active type (light-emitting type) and a passive type (light-accepting type) are known. The active type includes CRT (Cathode Ray Tube), PDP (Plasma Display Panel), ELD (Electroluminescence Display/EL Display Device), VFD (Vacuum Fluorescent Display), LED (Light-emitting Diode), or the like. On the other hand, the passive type includes LCD (Liquid Crystal Display), ECD (Electrochemical Display), EPID (Electro Phoretic Image Display), SPD (Suspended Particle Display), TBD (Twisting Ball Display), PLZT (Transparent Ceramic display using the strong dielectric PLZT [(Pb, La)(Zr, Ti)O3]), or the like.
The EL display device (ELD) or an EL element, which constructs the ELD, has a high visuality because of the self-emission, and the high durability against the shock because they are completely solid. Therefore, the development of various EL display devices is in progress now, in which inorganic and organic compounds are used in emitting layers. Among them, an organic EL display device, wherein an organic compound is sandwiched between two electrodes, is strongly expected as a display that can very efficiently and very brightly emit light of various kinds of colors because of the variety of organic compound.
Therefore, methods for constructing a full-color organic display device have been keenly developed. For example, Japanese Patent Laid-open Publication No. Hei8-264828 discloses a method to emit each of different colors (e.g. three primary colors of red, blue, and green) by plane and discretely placing the emitting parts of the organic EL display device.
There were problems, however, that it is necessary to newly develop emitting materials for each color to plane and discretely place emitting parts of the organic EL display element, and to display by emitting light of different colors, and that it has a low durability to a process (e.g. photolithography), in which it is plane and discretely placed, because the material per se is an organic compound.
Therefore, a method to decompose or modulate monochrome light through a color modulating layer (e.g. a color filter or a fluorescent layer) has been proposed (Japanese Patent Laid-open Publication No. Hei3-152897). This method is excellent in the point that it can be simply constructed because providing only a single color as an emitting layer is enough.
There are, however, some gaps between an organic EL element and a color modulating layer or between color modulating layers because it is necessary to provide a color modulating layer in addition to the organic EL element. Therefore, from these gaps light from the organic EL element or light from the light-modulating layer leak, and the viewing angle became narrow (i.e. color shift), giving an organic EL display device with a low visuality.
Thus, Japanese Patent Laid-open Publication No. Hei5-94878 discloses an EL display device in which a transparent resin layer is provided between an EL element and a color filter, with the thickness of the transparent resin layer being thinner than the distance between pixels of the EL element (See FIG. 15).
The problem of viewing angle has not been adequately solved, however, because there is no shading layer in such constitution, and leak of light from the side surface of the color filter layer can not be controlled. In addition, in case a fluorescent layer is used instead of the color filter layer, the fluorescent pigment(dye) more isotropically fluoresces, and as a result, leak of light becomes large, and a visuality became inferior.
In Japanese Patent Laid-open Publication No. Hei5-258860, is disclosed a multi-color luminescence way that luminescence of an organic EL element can be received (See FIG. 16).
The problem of viewing angle has not been adequately solved, however, because no shading layer between fluorescent media is shown in such constitution.
In Japanese Patent Laid-open Publication No. Hei5-94879, is disclosed an EL panel in which a spacer, which has a shading property and nearly perpendicularly projects against the substrate surface of the EL element, is provided, and a color filter is placed oppositely (See FIG. 17).
Although there is no problem concerning viewing angle in this case, the relation between the thickness of the shading layer and that of the color modulating layer and the relation between the distance from the organic EL element to the shading layer and the width of the shading layer are not taken into account, therefore such a problem occurred that an organic EL display device could not be constructed practically.
In Japanese Patent Laid-open Publication No. Sho63-40888, is disclosed a color display in which an EL element and a color filter are placed oppositely (See FIG. 18). In such constitution, however, the relation between the thickness of the shading layer and that of the color modulating layer, and the relation between the distance from the organic EL element to the shading layer and the width of the shading layer, are not taken into account, therefore such a problem occurred that a full-color EL display device could not be constructed practically.
The present invention was conceived in view of the above problems. It is therefore the object of the present invention to provide a practical organic EL display device that is excellent in a viewing angle property and a visuality, and allows a prevention of occurrence of color shift (color-mixing).
In the organic EL display device according to the present invention, a color modulating member composed of shading layers and color modulating layers, and an organic EL luminescent member composed of organic EL elements, are placed sandwiching a transparent medium to achieve the above-mentioned purpose, satisfying the relation d2xe2x89xa7d1, with d1 being the distance between the color modulating member and the organic EL luminescent member; d2 being the width of the shading layer.
In case the organic EL display device is constructed according to the present invention, it is preferred to construct the color modulating member with different kinds of color modulating layers.
In case the organic EL display device is constructed according to the present invention, it is preferred to construct the color modulating member with one kind of a color modulating layer.
In case the organic EL display device is constructed according to the present invention, it is preferred to satisfy the relation T1xe2x89xa7T2, with the thickness of the shading layer being T1; that of the color modulating layer being T2.
In case the organic EL display device is constructed according to the present invention, it is preferred to satisfy the relation |T1xe2x88x92T2|xe2x89xa62.0 xcexcm, with T1 being the thickness of the shading layer; T2 being that of the color modulating layer.
In case the organic EL display device is constructed according to the present invention, it is preferred to satisfy the relation S2xe2x89xa7S1, with S1 being the area of the luminescent region of the organic EL element; S2 being that of the color modulating layer.
In case the organic EL display device is constructed according to the present invention, it is preferred to construct the color modulating layer from a fluorescent layer.
In case the organic EL display device is constructed according to the present invention, it is preferred that the coat thickness of the color modulating layer is equal to or thicker than 5 xcexcm.
In case the organic EL display device is constructed according to the present invention, it is preferred to satisfy the relation |n1xe2x88x92n2| less than 0.4, with n1 being the refractive index of the color modulating layer; n2 being that of the transparent medium.
In case the organic EL display device is constructed according to the present invention, it is preferred to gradually or stepwise reduce the width of the shading layer from the transparent medium side to the opposite side.
In case the organic EL display device is constructed according to the present invention, it is preferred that the transmittance of light in the visible region of 400 nm to 700 nm of the shading layer is 10% or less.
In case the organic EL display device is constructed according to the present invention, it is preferred that the reflectance of light in the visible region of 400 nm to 700 nm of the shading layer is 10% or more.